Urea nitrogen recycling and the incorporation of orally administered 15N-ammonia into multiple plasma amino acids will be evaluated in (1)normal volunteers, 2) cachectic patients without cancer who have lost more than 10% body weight, 3) patients with stage III or IV orophayrngeal cancer who have been weight stable, 4) patients with stage III or IV orophayrngeal cancer who have lost more than 10% body weight. Stable isotope infusion studies will be performed on inpatients in the CRC after maintenance on a controlled liquid formula diet.